As somebody who started in the days of cgi-bin and SSIs, I've lost track of how many wheels I've seen re-invented over the past 25 years. Fortunately I do backend which is at least slightly more stable (modulo the fact that I'm sending more or less opaque-to-me javascript rather than html).

OTOH I have really surprised some PMs by producing a Perl cgi wireframe site during the course of the meeting where we designed the wireframe so we could actually try it. It's a skill more devs should really have in their back pocket.